This application is related to Japanese patent applications No. HEI 10-340931 filed on Oct. 23, 1998 and No. HEI 11-206626 filed on Jun. 15, 1999 whose priorities are claimed under 35 USC xc2xa7119, the disclosures of which are incorporated herein by reference in their entireties.
1. Field of the Invention
The present invention relates to a non-invasive living body measuring apparatus and method, and more particularly to a non-invasive living body measuring apparatus and method for analyzing image information obtained from a living body irradiated with light to obtain living body information such as morphology of a living body or concentration of a living body component.
2. Description of the Related Art
International Publication No. WO97/24066 discloses an apparatus for measuring a living body component such as hemoglobin without collecting blood (i.e., in a non-invasive manner). In the apparatus, a finger is positioned at a detecting section to capture a transmitted image of the finger, an analysis region (a blood vessel site with good contrast) is set in the image, and the analysis region is analyzed to calculate hemoglobin concentration.
When the finger is removed from the detecting section and placed again at the detecting section, the position of the finger may be different from its previous position. This allows the obtained captured image to be shifted in a right-and-left direction or in an up-and-down direction, rendering it difficult to measure the same site of the living body repeatedly. Therefore, this apparatus maybe unsuitable for measuring the change with time (time-sequential change) in the blood vessel width or the concentration of the living body component on a specific blood vessel site.
For example, Japanese Unexamined Patent Publication No. HEI 07(1995)-21373 discloses an apparatus for personal identification by picking up characteristic points (end points and branching points) from a blood vessel pattern obtained from a captured blood vessel image and using the positional arrangement of the characteristic points, the directional vector of the blood vessel, the linked state among the characteristic points and their combination as characteristic quantities. However, this publication does not disclose any solution to the problem of the shift of the living body in a non-invasive living body measuring apparatus. The publication merely discloses that xe2x80x9cIt might be expected that the direction of the finger may be shifted between the time of registration and the time of verification, so that a predetermined allowance (tolerance) range may be provided at the time of comparison for the personal identificationxe2x80x9d.
On the other hand, an image processing technique is known in which an image is binarized (digitized) in trying to extract a characteristic feature from the image having a density blur. However, no image processing technique is known which gives an explanation in relation to the above-mentioned problem of the shift of the living body in a non-invasive living body measuring apparatus.
Thus, an object of the present invention is to provide a non-invasive living body measuring apparatus capable of measuring the same site on the same living body even if the positional relationship between the living body and the apparatus may vary.
The present invention provides a non-invasive living body measuring apparatus comprising: a light source section for irradiating a portion of a living body; an image capturing section for capturing an image of the irradiated portion of the living body; a data processing section for setting an analysis region in the captured image to obtain information on the living body and for extracting a characteristic pattern from the captured image; an output section for outputting the obtained information on the living body; and an operating section for operating at least one of the image capture, data processing and output sections, wherein when the image capturing section captures first and second images of a portion of a living body at different times and the data processing section extracts first and second characteristic patterns from the first and second images, respectively and set an analysis region in the first image, the data processing section sets an analysis region in the second image basing on a relative shift amount of the first and second characteristic patterns requisite for matching the first and second characteristic patterns to each other.
To explain it in more detail, it is assumed that a first captured image G1 and a second captured image G2 are given, where an analysis region A1 has been set on the first captured image G1 and an analysis region A2 has not been set on the second captured image yet. Characteristic patterns H1, H2 are extracted from the captured images G1, G2, respectively, and a relative shift amount xcex94 required in obtaining a good match of the characteristic patterns H1, H2 is determined. The position of the analysis region A2 on the captured second image G2 can be determined by using the position of the analysis region A1 on the first captured image G1 and the above-mentioned relative shift amountxcex94.
In this manner, the same site of the living body may be set and measured as an analysis region on the different captured images obtained from the same living body, whereby the reproducibility of the information on the living body may be improved and the change of the information with time may be measured.
In another aspect, the present invention provides a non-invasive living body measuring method comprising the steps of: irradiating a portion of a living body with light; capturing an image of the irradiated portion of the living body; setting an analysis region in the captured image to obtain information on the living body and for extracting a characteristic pattern from the captured image; and outputting the obtained information on the living body; wherein when first and second images of a portion of a living body is captured at different times and first and second characteristic patterns are extracted from the first and second images, respectively and an analysis region in the first image is set, an analysis region in the second image is set basing on a relative shift amount of the first and second characteristic patterns requisite for matching the first and second characteristic patterns to each other.